Duo-servomotor valve means



Jan. 27, 1970 R. M. WALLIS 3,492,053

' DUO-SERVOMOTOR VALVE MEANS Filed March 6, 1968 2 Sheets-Sheet 1 gr II1 I I I m S N JL \3 Q E U h H 1 Q a F; g I! Q \9 LL \9 L If) 2%" s aWEN w I v u r V 3mg 3 (910 5' *2 A9 5 Q N g N INVENTOR.

ROBERT M. WALLIS QmQ/xm ATTORNEY R. M. WALLIS DUO-SERVOMOTOR VALVE MEANSJan. 27, 1970 2 Sheets-Sheet 2 Filed March 6; 1968 %M NR mm d QR W N} N3 @N Q Q: s g 3 Q w N9 25: 9% QM Nw nw QQ .a g g E QQQ NQ a Q a! N\E QQm w: Wm; mm

INVENTOR. ROBERT M- WALUS A RNEY United States Patent 3,492,053DUO-SERVOMOTOR VALVE MEANS Robert M. Wallis, South Bend, Ind., assignorto The Bendix Corporation, a corporation of Delaware Filed Mar. 6, 1968,Ser. No. 710,952 Int. Cl. B60t 13/56 U.S. Cl. 303-13 9 Claims ABSTRACTOF THE DISCLOSURE A valve device for controlling the operation of'one ormore differential pressure servo devices from a duo-hydraulic actuatorincorporating primary and secondary pz'ston elements with the secondarypiston elements being operatively connected to the primary pistonelement such that it is ineffective until a failure of the primarypiston element to actuate the valve means.

It has been observed that in controlling remote servomotor systems froma tandem actuator such as a split master cylinder in a vehicle brakingsystem that because of the very fact that the pressures delivered by thetandem actuator from its primary chamber and its secondary chamber arenot equal, the servomotor has a control problem. Furthermore, it hasbeen observed that it is possible to have a problem of high hysteresiswith such a system.

Such systems are observed in prior art Patents Nos. 3,268,270 and3,362,756, as well as Italian Patent No. 611,675.

It is the intent of this invention to provide a control valve for suchsystem which incorporates the fail-safe characteristics of the prior artdevices while at the same time eliminating the problems aforementioned.

Description Other objects and advantages of this invention will appearto those skilled in the art to which it relates from the followingdescription of the drawings in which:

FIGURE 1 shows a servomotor-system actuating device in schematic formwith which this invention is concerned; and

FIGURE 2 shows a cross section of the control valve for the servomotorsystem'of FIGURE 1 incorporating the elements of this invention.

With reference now to FIGURE 1, there is shown a master cylinder 10operable by a brake pedal 12 to create separate fluid pressures forconduits 14 and 16 communicating the master cylinder 10 to a 'valvemeans 18.

The valve means 18 is provided with an atmospheric inlet to which isconnected a conduit 20 leading. from an air cleaner or the like. Avacuum inlet via:a tube 22 is provided to valve means 18. Tube 22 isconnected to a fitting 24 which permits the joinder of a branch conduit26 that is, as the legend in FIGURE 1 indicates, connected to the engineintake manifold for the vehicle. Other branches 28 and 30 from thefitting 24 communicate the vacuum from the'engine intake manifold orfrom a' vacuum reservoir, as may be the case, to vacuum chambers withinthe housing 32 of the servomotor boost section.

Also the valve 18 is provided with a control discharge port to which afitting 34 is joined which in turn joins a control conduit 36 to thisport. The control conduit 36 communicates to the central chamber of thehousing 32 of the booster section of the servomotor.

While the details of the booster construction are not considered part ofthis invention, it will be realized by those skilled in the art to whichthis invention relates that the housing of the booster section 32 of theservomotor is constructed so as to have two diaphragms internallythereof dividing each half into a vacuum chamber and a control chamber.The control chambers are communicated via an opening through the housingat the center portion thereof to essentially provide one control chamberwith two independent movable walls controlled thereby. The servomotor iscompleted by the provisions of slave hydraulic cylinders 40 and 42 whichare internally provided with hydraulic pistons controllable by thediaphragms in the booster section for the development of pressures toconduits 44 and 46 leading to, respective, wheel cylinders 48 and 50 forbraking mechanisms of separate axles of the vehicle in which thisservomotor is associated. It should also be noted before passing on tothe specific construction of the valve 18 that the conduits 14 and 16are communicated to inlet ports 54 and 52 to actuate the inernal valvingmechanism hereinafter described in detail. The valve 18 also hashydraulic discharge ports 56 and 58 to which conduits 60 and 62 areconnected. These conduits 60 and 62 lead to ports 64 and 66 in therespective slave cylinders 40 and 42 to provide fluid compensation forthe slave cylinders as well as limited manual braking capability in theevent of a power failure of the booster section of the servomotor.

Turning now to the specific details of construction of the control valve18 with reference to FIGURE 2, there is shown a valve housing comprisingtwo portions 68 and 70 that are joined together, as at 72, by aplurality of radial bolts (not shown). At the juncture of the housingmembers 68 and 70 a bead 74 of a diaphragm 76 is compressed between thesections 68 and 70 to seal the assembly. As seen, the housing member 70includes a reference fluid low presure port 78, the vacuum port for theattachment thereto of conduit 22 of FIGURE 1. The housing member 68 isprovided with an atmospheric air or high pressure inlet port 80 to whichthe conduit 20 having flange 82 is assembled by means of snap ring 84.In addition, the housing member 70 comprises the hydraulic inlet ports52 and 54 as well as the hydraulic discharge ports 56 and 58. It may bereadily observed that the ports 52 and 56 are connected together via abore 86 in the housing 70 as are the ports 54 and 58. A pair of pistons88 and 90 are slidably arranged in the bore 86 with a floating piston 92therebetween. All of the pistons have fore and aft facing seals toprevent communication of fluid from one face thereof to the other facethereof. As seen, the bore 86 is a stepped bore that has a reduceddiameter portion 94' for the piston 90; whereas its large diameterportion 96 contains both the piston 88 and the floating piston 92. .Thebore 86 is provided with a stop plate 98 held in the open end thereof,as by snap ring 100 to limit the distance that the piston 88 can travel.Piston 88 is provided with a recess in its left face, as seen in thedrawing, to receive a stem 102 of a valve plunger 104 that is heldwithin the housing of the control valve 18 by the diaphragm 76 beingclamped in a recess in the plunger 104 by a spring retainer 106 so as toreset against a radial flange 108. The valve plunger 104 has a passage110 through it so as to communicate the vacuum chamber 112 with thecontrol chamber 114 in the attitude shown in FIGURE 2 where the returnspring 116 has, via the valve plunger 104 and its stem 102, retractedthe piston 88, 90 and 92 to their extreme right position within the bore86 of the housing section 70. The forward face of the valve plunger 104is provided with an annular valve seat 118.

The housing'member 68 is provided with an inwardly positioned collar 120which supports and guides the plunger 104 in its reciprocatory movementwithin the control valve 18. As seen the plunger 104 is further formedso as to provide a passage 122 at spaced intervals between it and thecollar 120 for fluid communication into the control chamber 114. Thecollar 120 is provided with a fixed valve seat 124 facing theatmospheric port 80, and plate 82 provides a bearing for spring 126 foroperatively urging a resilient valve seat 128 onto the seat 124 of thecollar 120. In addition a spring 130 is operatively arranged between theplate 82 and a central valve 132 for urging it onto the resilient valve128- about the central opening in valve 128. The valve 132 has a stem133 extending through the opening to which a disc 134 is connected overwhich a resilient valve seat 136 is snap fitted such that the disc 134and seat 136 extend along a line at an angle to the plane of contact ofthe rubber poppet 128 with the valve seat 124 on the same side of valve128 as seat 124.

The description of the construction of the valve 18 is then completed byreferencing the control discharge port 140 which in FIGURE 1 receivesthe fitting 34 for joining the conduit 36 leading to the controlchambers of the booster section of the servomotor therewith. Also thehousing section 70 is provided with a bleed opening 142 which is betweenthe abutting connection of the floating piston 92 and the small diameterpiston 90 so that fluid leakage by the floating piston 92 from theprimary chamber 144, or by the piston 90 from the secondary chamber 146will be vented to atmosphere and not be able to provide fluid blockagefor hindering the operation of the valve 18.

Operation In the operation the operator of the vehicle will depress thebrake pedal 12 to generate separate pressures for the conduits 14 and 16leading to the inlet ports 52 and 54 of the control valve 18. However,as will be readily realized by those skilled in the art to which thisinvention relates, the split master cylinder 10, while providingseparate fluid pressures, provides unequal fluid pressures. It developsa greater pressure from its primary chamber connected to the conduit 14than is normally possible from its secondary chamber connected to theconduit 16. However, as it is possible that a master cylinder of thetype as that shown in FIGURE 1 could be designed to have substantiallyequal pressure developments, the invention aforedescribed is stillapplicable to provide fail-safe operation of the valve 18 whileeliminating unnecessary moving parts during normal operation. As seen,the pressure from the primary chamber connected to the conduit 14 isintroduced to inlet 52 to act upon the piston 88 and the floating piston92. At the same time the pressure from chamber 16 enters inlet 54 to actupon the smaller diameter piston 90. As the diameters of the piston 88and 90 are different, the pressure in the primary chamber 144 of thecontrol valve 18 will not only actuate piston 88 but because of thelarge effective area of the floating piston 92 withhold the actuation ofpiston 90 thereby eliminating the need of movement of the piston 90during normal operation.

In any event as the pressure in primary chamber 144 acts upon the piston88 it causes the valve plunger 10.4 to abut its valve seat 118 on theangular face of the rubber seat 136. This causes a tilting of the valve132 to gradually introduce atmospheric pressure from the conduit 20 intothe control chamber 114 and via the control discharge port 140 to thecontrol chambers of the boost section of the housing 32 of theservomotor. As pressure is increased by the master cylinder 10, thevalve plunger 104 will eventually cause the unseating of the rubber seat128 from the seat 124 on the collar 120. At this point full atmosphericpressure is being fed to the control chamber of the booster section sothat maximum pressure may be developed independently by the slavecylinders 40 and 42 for the wheel cylinders 48 and 50 of the separatebraking systems of the vehicle.

In the event of a failure in the primary side of the master cylindercausing a loss of pressure in the conduit 14, the secondary chamber ofthe master cylinder will via the conduit 16 introduce pressure to thesecondary chamber 146 of the valve 18. As there will be no resistingpressure via the floating piston 92, piston will actuate the valve inthe manner aforementioned.

I claim:

1. A valve device for controlling the operation of servo devices of thedifferential air pressure or vacuum type, which valve device comprises:

a housing;

valve means at one end of said housing;

piston means within a bore of said housing operatively connected to saidvalve means, said piston means including a first piston and a secondpiston of lesser effective area than said first piston; and

a means between said first piston and said second piston in fluidcommuication with said first piston and of an equal effective area assaid first piston and operatively connected to said sec-0nd piston towithhold the operation of said second piston so long as said firstpiston is controlling said valve means.

2. A valve device according to claim 1 wherein each valve means includesa pressure responsive reaction member adapted to transmit reactionforces to said piston means during the operation of said valve means.

3. A valve means operable by single and multiple input forcescomprising:

ahousing including a valve chamber and a longitudinal bore;

a first piston in said longitudinal bore having seal means effective toprevent communication of fluid pressure from one side of said firstpiston to the other side of said first piston and vice versa, said firstpiston being of a predetermined effective area;

a second piston in said bore having seal means preventing fluidcommunication between one end of said second piston and the other end ofsaid second piston and vice versa, said second piston having a lessereffective area in said bore than said first piston;

a third piston between said first and second pistons in said bore, whichthird piston is subjected to fluid pressure controlling said firstpiston to be effective to withhold said second piston so long as fluidpressure is delivered to said first piston; and

a valve in said housing operatively connected to said first piston forcontrolling communication of a reference fluid pressure and a controlfluid pressure to a valve control port of said housing.

4. A valve means according to claim 3 wherein said valve is mounted insaid housing by a diaphragm to provide reaction forces for said first orsecond pistons, as said valve is operated.

5. A valve according to claim 3 wherein said valve I may be furthercharacterized as including:

a first valve seat formed on said housing;

a plunger slidably guided by said housing and having a second valve seaton the forward end thereof which is arranged in said housing to the rearof said first valve seat so as to be movable toward said first valveseat, said plunger including a rearwardly projecting stem operativelyconnected to said first piston in said longitudinal bore, said plungeralso having a longitudinal passageway therethrough;

a poppet means comprising an annular surface for abutment with saidfirst valve seat and a second surface operatively connected to saidannular surface arranged to be abutted by said second valve seat as itmoves in a direction of said first valve seat, said second surface beingspring biased to the rear of the first surface and being operativelyconnected to a spool valve adapted to control an opening through thefirst annular surface, said second surface and said second valve seatbeing constructed so as to abut on an angle with respect to a planepassing through the abutment of said first annular surface on said firstvalve seat of said housing; and

a means biasing said plunger so that said second valve seat is normallynot in contact with said second surface so that reference pressure iscommunicated to said valve means via said passage through said plungerand said control pressure is prevented from communication to said valvecontrol port by said valve mechanism.

6. A valve means according to claim 3 wherein said housing has anexterior vent leading into said bore to be between said third piston andsaid second piston to prevent fluid entrapment and blockage of thecontrol of said second piston by said third piston.

7. A valve device for controlling the operation of servo devices of theditferential pressure type comprising:

a valve body with a bore therein having a first hydraulic inlet port anda second hydraulic inlet port as well as a control pressure inlet port,a reference pressure inlet port and a control pressure discharge port;

a pair of valve actuating pistons disposed in said bore, one of which isof lesser effective area than the other, which pair of valve actuatingpistons are interconnected by a floating piston having an eifective areaequal to that of the larger of the pair of valve actuating pistons,which pair of valve actuating pistons are independently connected tosaid first hydraulic inlet port and said second hydraulic inlet port;and valve means operatively connected to at least one of the pair ofsaid valve actuating pistons and within said housing to be between saidcontrol pressure inlet port and said reference pressure inlet port andthe control discharge port of the housing.

8. A valve device according to claim 7 wherein said bore in said housingcontaining said pair of valve actuating pistons is a stepped bore.

9. A valve device according to claim 8 wherein said valve means isfurther characterized as including a pressure responsive reaction memberfor providing reaction forces to said pair of valve actuating pistonsduring the actuation of said valve means after said control pressureinlet port has been communicated by said valve means to said controlpressure discharge port of said housing.

References Cited UNITED STATES PATENTS 3,268,270 8/1966 Bailey 3133,362,756 1/1968 Brandon 30313 2,299,211 10/1942 Clench 9262 X 2,577,46212/1951 Hackney 9261 X MILTON BUCHLER, Primary Examiner JOHN J.MCLAUGHLIN, JR., Assistant Examiner US Cl. X.R.

